Question

Can someone please help me out with the Rf value PLEASE!!

Thin Layer Chromatography Procedures 1) Prepare a solvent solution in a 150 mL beaker by using 5 mL of Hexane and 3 mL of ethyl acetate Take one plate and spot (small spots) it with the three different standard solutions given. The standard solutions are 2-nitroaniline, 3-nitroaniline, and 4-nitroaniline. The fourth spot will be the unknown sample obtained. 2) 3) Align these spots at 1 cm from the bottom of the plates 4) Using tweezers, slowly introduce the plate into the beaker making sure that only the top back edge of the plate touches the wall of the beaker. The solvent must be below the level of the spots. If the spots are below the solvent, the compounds will dissolve in the solvent. 5) Cover the beakers with a watch glass 6) Let the plates develop by allowing the solvent to travel up.the plates by capillary action. Different compounds will move up at different speed due to the difference in structure. The yellow colors of the compounds will appear at different height on the plates. When the solvent reaches the top, carefully remove 7) the plate, and quickly mark the top of the sol lvent line with a pencil. Then put the plate in the hood to let the solvent evaporate. Data: Distance traveled by the solvent (em: 5.5 Rr value Color Compounds Distance Traveled (cm) 2-Nitroaniline 3-Nitroaniline 4-Nitroaniline Unknown Spot 13.2

Answer 1

RF value is defined as the ratio of distance moved by the solute and the distance moved by the solvent. The distance moved by the solvent is also called as solvent front.

Rf = distance travelled by the solute/distance travelled by the solvent

I) 2-nitroaniline: Rf = 3.8÷5.5 = 0.69

ii) 3-nitroaniline: Rf = 3÷5.5 = 0.54

iii) 4-nitroaniline: Rf = 2.3÷5.5 = 0.42

iv) unknown spot: Rf = 3.8÷5.5 = 0.69

Please note that all the values are rounded off to two decimal places.